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Current Electricity
1. When no current is flowing through a conductor
then
(1) All free electrons are moving in such a way,
so that average speed is zero
(2) All free electrons in conductor are in rest
(3) Average thermal velocity of free electrons is
zero
(4) All of these
2. The expression for thermal speed of free electron in
a conductor is
kT
k T m
k T m
3 kT
m
3. When no current is flowing through the conductor,
free electrons are in state of random motion and
they collide among each other. Path of an electron
between two successive collisions is
(1) Curved
(2) Straight line
(3) Sometime curved & sometime straight line
(4) None
4. Electric current through a conductor varies with
time as i = at
2 where a is a constant. Total charge
flown through a cross-section in time t 1 = 0 to t 2 =
2 sec is
a unit
a unit
a unit
(4) a × 8 unit
5. Charge through a cross-section time graph is shown
in the figure. Current at t = 4 sec is equal to
(1) 1 A (2) 0.5 A
(3) 1.5 A (4) 0
6. The charge flown through a cross-section of
conductor, in time t 1 = 2 to t 2 = 6 sec is
(1) 2C (2) 4C
(3) 6 C (4) Data insufficient
7. If current through a cross-section varies with time
as i = ( a + bt ) where a and b are constant, then
average current through the cross-section in time t 1
= 0 to t 2 = 2 sec is
(1) ( a + 2 b ) (2) (2 a + b )
(3) ( a + 2
b ) (4) ( a + b )
8. The unidirectional current that is assumed to be
flowing through a conductor from high potential to
low potential, is known as
(1) Alternating current
(2) Electronic current
(3) Conventional current
(4) All of these
DPP- 01
9. Select the correct statement regarding current
(1) Its dimension is [M
0 L
0 T
0 A]
(2) It is a scalar quantity
(3) It’s SI unit is ampere
(4) All of these
10. Select the correct statements regarding current
density
(1) It is a vector quantity
(2) It’s SI unit is A/m
2
(3) It’s dimensions are [M
0 L
0 A]
(4) I = j dA
11. Find the number of free electrons per unit volume
in a conductor, whose density is 10
4 kg/m
3
. Atomic
mass number is 100 and every atom contribute one
free electron.
(1) 6.023 × 10
8 /m
3 (2) 6.023 × 10
18 /m
3
(3) 6.023 × 10
23 /m
3 (4) 6.023 × 10
28 /m
3
12. 20,000 α-particle are passing through a tube
(diameter 2 cm), per minute. The current through
the tube is
(1) 32 × 10
× 10
× 10
13. Charge carriers in semi-conductor, is/are
(1) Only free electrons
(2) Only holes
(3) Both free electrons and holes
(4) None
14. Which of the following is correct statement(s)
(1) On increasing temperature number density of
conduction electrons increases in semi-
conductor & insulator
(2) On increasing temperature relaxation time
decreases in metallic conductor
(3) On increasing temperature relaxation time
increases in metallic conductor.
15. Charge is flowing through a uniform conductor,
which varies with time as shown in the figure. The
current in conductor at t = 3 sec is
(1) 4 A (2) 3 A
(3) 12 A (4) 8 A
16. Select the correct expression for drift velocity of
conduction electrons in metallic conductor.
(Symbols has their usual meanings)
d
eE v m
(2)^2
d
eE v m
d
eE v m
(4)^2
d
eE v m
17. Resistivity of a metallic conductor is given by
2 me
n
2 me
n
2
m
ne
2
m
ne
18. In metallic conductor, resistivity increase with
increase in temperature because
(1) On increasing temperature ‘ n ’ decreases
(2) On increasing temperature ‘τ’ decreases
(3) On increasing temperature ‘ m ’ increases
(4) Both (1) and (2)
19. Two wires of same cross-sectional area are
connected in series. If ration of number density of
conduction electrons in two wires is 3 : 2 then ratio
of drift velocity of conduction electrons,
(when i current flows), is
Answer Key
